The present invention relates to a detachable motor drive for a bicycle. More particularly, this invention relates to a detachable motor drive for a bicycle, which is easy to attach to or detach from a bicycle, and does not interfere with the drive train of the bicycle.
Many motor drive devices, which aid driving a humanpower-driven bicycle, have been developed. Such devices use an electric motor, or a small gasoline engine to provide driving force to a bicycle. Such devices are useful when riding on a bicycle on an inclined road, or riding on a bicycle for a long distance.
As an example of motor drive for a bicycle, U.S. Pat. No. 5,491,390 to McGreen discloses an electric propulsion system for a bicycle, which includes an electric motor secured to a mounting assembly, a drive roller that impinges on the front wheel of the bicycle, and a battery pack secured to the frame of the bicycle.
U.S. Pat. No. 6,155,369 to Whittaker discloses an electric bicycle, which includes a DC motor, a clutch, and drive circuitry. The motor's driving power is transferred to the rear wheel of the bicycle via a chain or V-belt transmission.
U.S. Pat. No. Des. 434,349 to Currie et al. discloses an electric bicycle with pedal torque enable unit, which includes a battery unit carried in the triangular space between the frames of the bicycle, and a motor that engages with the sprocket wheel of the rear wheel.
U.S. Pat. No. 6,516,911 to Mayer et al. discloses a unitary power module for electric bicycles, which includes a target sprocket that can be attached to the axle of either the front wheel or the rear wheel, and a pinion sprocket that engages with the target sprocket, and is driven by a motor.
U.S. Patent Application Publication No. US2002/0027026 to Hong discloses an automatic transmission for electric bicycle, which includes a motor, a friction wheel that engages with the rear wheel of a bicycle, a power-transmitting device, and an electronic gearshift device.
Disadvantages of motor drives for a bicycle by prior art are that they include many parts and thus are expensive; that they are integrated with the manual drive train of the bicycle, or engage with either wheel of the bicycle, and thus are difficult to install or uninstall; and that they are usually positioned in the middle of or in the upper part of the bicycle, and thus it is hard to balance the bicycle since the center of gravity is high.